I've posted about a few of these before, but I'd like to make one list of the various weapon and mechanics errors I've spotted in the game. Most of these are pretty minor, though in some cases that's exactly why they bother me. Sandstorm has, by far, the best weapon handling in any game I've ever played. It's awesome, but to me it does make the small errors that remain stick out all the more.

G-36K
The normal reload from empty is correct, with the locked-back bolt being released with the charging handle. The speed reload from empty uses some other mechanism to release the bolt though, and I'm not sure what. On a stock rifle, there is no other option to release the bolt. There is an aftermarket part that replaces the bolt locking button inside the trigger guard with a catch that allows releasing the bolt with the trigger finger, I'm not sure that it's a popular accessory and it seems weird for it to be on a rifle in game and only used in one reload animation.

I'm not aware of any extended magazines actually in existence for the G-36, so some alternative would be nice.

G-3A3
The speed reload as depicted is not physically possible. The arrangement of the magazine, magazine release paddle, and trigger guard make it impossible to actuate the magazine release with another magazine. The speed reload should be changed to look more like the G-36 reload where the magazine is released and cleared with the support hand thumb.

It would also be nice to see the optic rail removed when not mounting an optic, just like how the AK series does not always have a dovetail rail mounted to it.

M-4 and M-16 with M-203
I like the little variation on the reload when you have the GL attached. One slight problem: it's generally discouraged to use an open-hand slap to hit the bolt release. The palm of the hand is concave, and it's totally possible to slap the shit out of the side of the rifle and not release the bolt because the bolt release paddle ended up right in the center of the palm and didn't get pushed far enough. It's acceptable to use the meat of the thumb to hit it, this puts the support hand in a good possession to run forward after the reload, and this might be what happens in the reload animation, but it's hard to tell. A better option is using a closed 'hammer" fist to hit the bolt release, and this is closer to what is trained in the Army.

M-4 and M-16 with drum mag
This isn't technically an error, but why use the charging handle when reloading with a drum mag? It'll work, but it's slower and a bit awkward since with the bolt locked back there is no resistance on the charging handle until it engages the bolt carrier. Is it because there are reports of the bolt not locking back correctly after the last shot with some drums?

MP-7
The MP-7 uses a unique style of flip-up iron sight that resembles a pistol sight when folded down, but flips up to resemble something a lot more like traditional rifle flip-up sights. When running the gun with only irons your character uses it with the sights left down, which is not ideal. Why not have them flip up like every other weapon with flip-up sights?

AKSU-74
The standard OKP-7 cannot be mounted to the AKSU. The AKSU uses a different rear sight assembly which impacts the OKP-7's dovetail mount. It could probobly mount the railed version of the sight using a doevetail mount adapter though, just like how the EOTech and Aimpoint are mounted.

PK-AS
This is a 1x sight in reality, but I guess since it's a collimator making it 1.5X kinda makes sense in a game. More annoying - the reticule should be a non-illuminated black etched circle with a red-illuminated black etched dot in the center. Right now it mostly resembles the EOTech reticule, which is wrong. The PK-AS reticule should be perfectly sharp, not slightly fuzzy like the EOTech.

Staged Reloading
Any weapon what has a bolt or slide that locks open following the last shot, which means most of the rifles and all of the pistols, has a staged reloading issue: eject the magazine, then sprint or switch weapons, then come back to that weapon. It will have no magazine and a round in the chamber. You can fire a single shot with the weapon in that condition, the one that was left in the chamber, which is correct. But then the weapon will lock open as is typical for the empty weapon animation. This is not correct - any weapon which locks open after the last shot does so with a mechanism that is actuated by the follower in the magazine. Without a magazine, the weapon will cycle and close the breech on an empty chamber. Reloading from this state requires inserting a magazine, then manually cycling the weapon, which probobly means a new animation for these weapons. Luckily this is pretty close to the first-load animations, so it might be a pretty easy animation to add?

I also want to add that sometimes, fast reloading (dropping the mag) on some weapons, with a bullet in the chamber, still uses the reload animation, which assumes there's no round in the chamber.
I'm not sure which weapons are affected, but I've had that bug multiple times with the SCAR-H and an ACOG scope attached.
Even the magazine drawing showed multiple rounds still in the mag, meaning there was a round in the chamber.

Another bug is that you can't put an extra shell into shotguns.
For example let's assume you have a 7+1 tube capacity shotgun. You loud your 7 rounds, you cock the shotgun, now you have 1 in the chamber and only 6 in the tube, therefor you should be able to load one more.

Not really sure if the M24 can do the same, but I guess it should be able to.

Another bug is that you can't put an extra shell into shotguns.
For example let's assume you have a 7+1 tube capacity shotgun. You loud your 7 rounds, you cock the shotgun, now you have 1 in the chamber and only 6 in the tube, therefor you should be able to load one more.

The M-870 works correctly in the game. It has 7+1 capacity, you breach load a single shell, then load 7 more into the tube. The TOZ also has a correct animation of breach loading followed by tube loading, but loads to 6+1. Wikipedia says the TOZ-194 has a 7 round tube magazine, so this looks like an error, but I don't know enough about this shotgun in real life to comment on possible variants in mag size.

Though I did notice just now that your character doesn't pump after firing the last shell. Why is that? Does he magically know it was the last one and decide to leave the fired shell in the chamber? Why not eject it and keep the breach open until loading?

Not really sure if the M24 can do the same, but I guess it should be able to.

Sorta, but not easily. Unless using the model with a detachable magazine, there's no way to load the magazine without opening the bolt. You'd need to fully load the magazine, then breach load a round, and close the bolt while holding down the top round on the magazine. You usually have to really ram the bolt home while doing this too, as it doesn't line the casing up to slide easily past the extractor.

I always thought that deploy animation cocks the shotgun, meaning there would be a total of 7 shots in the shotgun, but I think it's not a fully shotgun cock, just an ammo check. That'd explain why I can't reload an extra shell.
Also I guess bolt action Sniper Rifles are kind of more realistic in this way. I mean you won't be holding down that bullet, just so you can shove that one extra bullet in on the battlefield.